Actually, Kenzan, 3, and 4 share the same engine. While 5, Ishin, Zero, Kiwami, and Hokuto Ga Gotoku share the same engine.
4 and 5 do look very similar, but it's mostly the direction of the cutscenes. It's pretty interesting stuff! I'm not sure if the different engines have names, besides the Dragon Engine, which is currently for the PS4 only games.

At the end it asks if you would buy the Fist of the North Star Yakuza game if it was localized.

Some sites considering this survey an all-but-confirmation that we'll get a Hokuto translation, despite the fact exactly the same question was asked in the survey they released just after the announcement of the game last year,

I think it'll happen, I hope it'll happen, but I bought it last month, anyway, and if it does come out in English next year... sure, I'll double dip.

Actually, Kenzan, 3, and 4 share the same engine. While 5, Ishin, Zero, Kiwami, and Hokuto Ga Gotoku share the same engine.
4 and 5 do look very similar, but it's mostly the direction of the cutscenes. It's pretty interesting stuff! I'm not sure if the different engines have names, besides the Dragon Engine, which is currently for the PS4 only games.

Hokuto Ga Gotoku runs on 5's engine? Really? I'm definitely surprised to hear that since it was announced late enough to where I would have thought it would use 6's like Kiwami 2.

Hokuto Ga Gotoku runs on 5's engine? Really? I'm definitely surprised to hear that since it was announced late enough to where I would have thought it would use 6's like Kiwami 2.

Yup, iirc it's because Yakuza 6's engine is hard to work with, and since the Fist of the North Star game's art style is unrealistic and cel shaded it's easier to have it look good in Yakuza 5/0's engine anyway. Also means it runs at 60fps, rather than it struggling to run at 30fps like Yakuza 6 does.

Most likely best to go with Kiwami. I've not played 6 because I actually want to play the games chronologically but it's up to you if you want to do that. As for Kiwami it's story isn't as good as Y0, it really shows how far the writing has come along since the first game but it's still enjoyable.

Shenmue 1 and 2 is not listed as having it yet, but this is the problem. As much as I want to support SEGA on PC, they are making it really fucking hard. For now I'll stick to the PS4 release because there is no way in hell I am supporting a company using Denuvo. The fact SEGA has been tone deaf enough to keep doing it after hearing our protests over MANIA is more than enough reason to tell SEGA to fuck themselves with this.